Baked cores for use in metal casting



PstentedMay9,l950 w e um'rso stares numconnsronussmmnoasrmof Burgess nwm, Brooklyn, N; Y., aflgner to Whitehead Brothers Company, New York, N. Y." a corporation of New Jersey No Drawing. Application May I, 1947, Serial No. 748,823

2 Claims. (Cl. 22-188) s 2 This invention relates to the casting of metals of carbon granules adhesively united with such a and more especially to the production of debinder orwhich core, at least throughout the enstructible cores for use in casting dimculty tire outer layer thereof to a depth at least about oxidizable metals, such as grey iron, steel, bronze 0ne-ei8hth inch below the surfaces thereof comand their alloys. prises such an agglomeration.

' principal objects of the invention are the In carrying out my invention, I preferably proand economical production of ceedas follows: I v a at:

, "forisuch metal casting purposes carbonaceous of'forming dimension-true holes r value of about 45% t: castings, the surfaces of which l0 residue when heated tow a smooth and entirely devoid of absence of air of at least grains, pits, cracks or other deweight, such as a coke, for Other objects of the invention are hereinand selectively 8 the aftersetforth. to the appropriate gram 1n the manufacture of foundry cores, it is now 15 the character of the particular job customary to form the same by bonding together, between about 50 and 250 grain na e into a core of the desired shape and size, particles as defined by the Foundry Sand Grading M a of fusible, refractory substances, such as sand cation of the American Foundrymen's Associagrains, for example, with organic binders as lintion. By a judicious blending of the various sizes seed oil, tung oil or the like, so-called cereal 2 of such grains in ordertoobtain the desired grain binders, synthetic resins, silicates, pitches and fineness number in the ground and sized coke, the like. The molded cores are then baked at an cores of any desired degree of permeability, such optimum temperature in an oven and usually as aforesaid, canbeobtained. Such carbonaceous while still hot, though sometimes when cool d, materials as anthracite coal of low ash content, a blacking coat of relatively insignificant thick- 2 coke, graphite and the like are especially desirable ness is either brushed or sprayed thereon or else for the production of any improved cores. The the cores are dipped into a suspension of the blended grains of the carbonaceous base are then blacking and allowed to drain. Not only are some intimately admixed with a binder, such as one or of the sand or other fusible particles so bonded more of the aforesaid standard binders, the together in such cores either actually present in .0 amount thereof being predetermined in the manor in such close proximity to the surface of the her now customary to produce'cores of the desired core that during a casting operation the molten strengt The core is then molded and baked metal will reach the same and burn them into in a standard core oven at an optimum temperathe surfaces of the resultant castings but the ture in the well-known manner such for example backing coat, itself, also tends to render as as described in Patents Nos. 913,574,1" 1,950 and to the size and to pattern shape. 1,531,871, in order todry e they isct that the biacklns that or soften the binder a m t h be very fine to remain in susare thoroughly mm H;

1 its vehicle results in the undue 0102- will I the hot f 1 n m by the hlsckinl with the con- 60 metalis poured aboutths r in the permeability thereof to mtillzable substances. "Another dhadvsntase result-ins from the use of .haitltcndency to peel or flake on on he to the different eoeiiicients of expans hebhckins and the uncosted core. such a, materially estimated it it be atis cont ct morethm In making composite cores. it is preferable to mold or press the mulled mixture of carbon granules and binder into the form of a hollow matrix of the external shape desired with a wall thickness of at least about y and desirably about depending on the size of core desired and then the cavity in such matrix is filled with molding sand, gravel, cinders or other cheap filler very loosely bonded together with a binder such as aforesaid, whereupon the resulting shape is baked in the manner aforesaid. The baked composite core will have sufiicient hot strength imparted thereto by the carbon matrix or shell thereof to be capable of resisting the erosive action of the hot metal while at the same time it will peel equally as well as if the entire core were composed of such agglomerated carbon granules.

It cannot be too strongly emphasized that my improved solid or composite cores have the combustible medium, 1. e., the binder element, simultaneously baked integral with the other components of the core, as contra-distinguished from the ordinary core wherein the carbon blacking is usually applied as a wash of relatively insignificant thickness to a previously baked core composed of silica sand or like refractory grains bonded together and which wash is usually not baked so as to become an integral fused part of such cores.

My improved cores of either of the specified types thereof can be readily disintegrated and removed from the castings produced therewith. since no blacking coat is required, there is a considerable savingin time and expense in the core making operation. These cores are of accurate dimensions, and due to the absence of any blacking coat there is nothing to peel off or flake oil! therefrom. Furthermore, in the composite type thereof the enveloping carbon layer or shell can be applied to any desired degree of thickness without deleteriouslydiminishing the gas permeability thereof. Since the core is composed either of carbon throughout agg'lomerate i by thew binder or at least to a very substantial depth below the surface, no molten metal can reach any sand or other frittable silicious particles during the casting operation such as invariably occurs when employing the ordinary sand cores above described. As a consequence. my improved cores perfectly face the area of the casting contacting therewith, thereby insuring the formation of dimension-true, clean holes whose walls are completely devoid of burnt-on sand or other fritted particles. Moreover, due to the fact that the blend of the grain sizes of the carbon employed can be of a definite predetermined or selected grain fineness number, it is possible to insure that such grains can be compacted to a maximum degree consistent with the gas permeability desired. The selected grains will have a maximum number of points of contact thus requiring but a minimum amount of binder to effectively cement the same together as compared with the amount ordinarily required in standard cores to produce a core of the desired strength or, in other words. my cores will possess an increased comparative strength as contrasted with the ordinary core if like amounts of binder are employed in both. My improved cores are suitable for use either in green, dry or baked molds.

The composite core" above described is especially economical to produce, since the sand or like cheap filler comprising the center thereof constitutes its major portion as the surface layer or shell is comparatively thin, being desirably one-quarter of an inch thick and not less than about one-eighth of an inch. Preferably the centers of these cores have a much weaker bond than the shell and accordingly they can be readily collapsed and disintegrated when it is desired to remove such cores from the casting and when the centers have been so disintegrated the shell can be easily collapsed and removed in fragments.

The organic binder in my improved cores, while it suffices to produce the requisite hot strength during casting of the metal, becomes consumed or decomposed to such an extent during such operation as to render the core easily disintegratable and consequently readily removable from the casting all in the manner now customary-and in this respect functions quite differently from sodium silicate and like inorganic binders such as commonly employed in the manufacture of socalled permanent molds.

While I preferably employ but between about 2% and 3% of the organic binder, larger amounts, depending upon the nature of the particular binder employed, may be used but in no event should the amount thereof be suificient to interfere with the requisite gas-permeability of the core or the ready disintegration and removal thereof from the casting.

The term matrix as used in the claims is intended to refer to the enveloping outer layer or shell of the composite core which envelops the filling thereof.

Various modifications of the herein described core composition and method, within the scope of the appended claims, may be made without departing from the spirit of my invention.

Having thus described my invention, I claim:

1. A baked core for use in casting metals, the same consisting essentially of a blend of grains of refractory carbon bonded together with a binder and which blend of carbon grains has a rain fineness number between about 50 and 250 ..as defined by the Foundry Sand Grading Classification ofthe American Foundrymens Association.

2. A baked core for use in casting metals, the same consisting essentially, at least as to the outer layer thereof to a depth of about one-eighth of an inch beneath its outer surface, of a blend of grains of refractory carbon bonded together with a binder and which blend of carbon grains has a grain fineness number between about 50 and 250 as defined by the Foundry Sand Grading Classification of the American Foundrymens Association.

BURGESS P. WALLACE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 174,356 Darling Mar. 7, 1876 422,055 Lytle Feb. 25, 1890 805,144 Kuller Nov. 21, 1905 1,165,651 Davis Dec. 28, 1915 1,316,471 Acton et al Sept. 16, 1919 1,467,112 Lucier Sept. 4, 1923 1,775,576 Waters Sept. 9, 1930 1,955,936 Wallace Apr. 24, 1934 2,306,883 Holmes Dec. 29, 1942 2,322,638 Kleeman June 22, 1943 

2. A BAKED CORE FOR USE IN CASTING METALS, THE SAME CONSISTING ESSENTIALLY, AT LEAST AS TO THE OUTER LAYER THEREOF TO A DEPTH OF ABOUT ONE-EIGHT OF AN INCH BENEATH ITS OUTER SURFACE, OF A BLEND OF GRAINS OF REFRACTORY CARBON BONDED TOGETHER WITH A BINDER AND WHICH BLEND OF CARBON GRAINS HAS A GRAIN FINENESS NUMBER BETWEEN ABOUT 50 AND 250 AS DEFINED BY THE FOUNDRY SAND GRANDING CLASSIFICATION OF THE AMERICAN FOUNDRYMEN''S ASSOCIATION. 